Wood forming method

ABSTRACT

Wood is plasticized for forming operations by treatment with loweralkyl amines containing one to two carbon atoms.

Elite States Patet n 1 Beall WOOD FORMING METHOD [75] Inventor: Francis C. Beall, State College, Pa.

[73] Assignee: Research Corporation, New York,

22 Filed: Aug.6,197l

21 Appl.No.: 169,865

[56] References Cited UNITED STATES PATENTS 2,414,808 1/1947 Hamill ..144/327 Feb. 20, 1973 5/1961 -Cilab ..264/83 ll/l966 Schuerch ..l44/327 Primary Examiner-Donald R. Schran Attorney-Harold T. Stowell et al.

[57] ABSTRACT Wood is plasticized for forming operations by treatment with loweralkyl amines containing one to two carbon atoms.

3 Claims, No Drawings WOOD FORMING METHOD This invention relates to an improved method for forming wood or wood products.

In the traditional procedure for forming or bending wood articles, wood is steamed at elevated temperatures or molded under pressure and then dried for an extended period of time while still subject to considerable pressure. More recently, U. S. Pat. No. 3,282,313 teaches that wood can be plasticized for forming by treatment with anhydrous ammonia. According to the patent, liquid ammonia is preferred whereas gaseous ammonia at ordinary temperature and pressure conditions and aqueous solutions of ammonia are ineffective as plasticizers.

It is a principal object of the present invention to provide an improved method for the forming of wood operative at ordinary or comparatively mild conditions of temperature and pressure.

It is a further object of this invention to provide a method for the forming of even relatively large pieces of wood which does not require the application of a significant amount of force to the wood being formed.

These and other objects and advantages of the present invention will become apparent from the following discussion and examples.

' The present invention is based on the discovery that wood can be plasticized for forming operations by treatment with lower-alkyl amines containing one or two carbon atoms, i.e., monomethylamine, dimethylamine and ethylamine.

More specifically, the present invention is a method for forming wood which comprises impregnating the wood to be formed with a lower-alkyl amine containing one or two carbon atoms, bringing the impregnated wood to a desired configuration and drying the wood while maintained in the desired configurations.

In practicing the method of the present invention, the article or piece of wood to be formed is first cut or otherwise prepared so as to have the desired size. The work piece is then impregnated, most conveniently by soaking in a tank or similar vessel, with a solution containing the lower-alkyl amine or by treatment with vapors of the amine. The impregnated work piece is then formed, bent or molded to the desired shape and maintained under sufficient restraint to prevent it from reverting to its original shape until dry. The article may be dried under ambient conditions; moderate warming and forced ventilation will accelerate drying and the evaporated amine can be recovered by conventional techniques for recycle to the impregnation step.

The essential step in the present method is plasticization by impregnation of the wood or wood article to be formed with a lower-alkyl amine containing 1 or 2 carbon atoms. Such amines are gases at ambient conditions but only a small amount of pressure is required to maintain them liquid at ordinary room temperature (25C). lmpregnation may be effected with amine vapor or liquid amine. The exact temperature of impregnation is not critical; operation at room temperature or under ambient conditions is most convenient and is readily accomplished using the amine in aqueous solution. The time required for impregnation will depend on the size of the work piece; several days is usually sufficient for even larger pieces. Once the wood has become plasticized by impregnation with the amine, only a minimum of force is necessary to form or bend the impregnated wood to a desired configuration. The configuration achieved is made permanent by maintaining the formed wood under mild restraint sufficient to hold new configurations until the volatile amine has evaporated. After the amine (and its plasticizing effect) is removed, there is no tendency for the dried article to revert to its original shape. Most wood formed according to the method of the invention is not darkened.

The following example illustrates the small amount of force required to form wood impregnated with a suitable amine according to the procedure of the invention.

Rotary-cut veneer strips of yellow poplar (12% moisture content) 3 mm thick, 17 mm wide and mm long were immersed at ambient conditions (22C) for 30 minutes in the impregnating solutions listed below (the amines are available commercially as their aqueous solutions). The impregnated strips were then placed under a torque of 600 dyne-cm (200 g load on a 3 cm arm), air-dried under torsion, and the resultant degree of twist recorded. As an indication of the permanence of the forming operation, the twisted strips of veneer were soaked for 24 hours in water, dried to 6 percent moisture content and the degree of twist remaining measured. The results obtained are sum- Since the 24 hour soak period in water provides ample opportunity for relaxation of stresses previously induced in the wood, the maintenance of appreciable twist post-soaking is particularly significant. I

Comparable results were obtained when birch wood strips were treated in a similar fashion.

The following example illustrates application of the method of the invention to larger pieces of wood.

Six pieces of red oak, about A inch thick, 1 V4 inches wide and 14 inches long, were immersed in various aqueous solutions containing 20-40 percent methylamine at 22C for 48 hours, twisted along the length by hand, and air-dried under restraint. The pieces of oak retained their new shape and original color.

The same general result was obtained when the method herein described was applied to various types of wood having an initial moisture content varying from 6 percent up to green.

Other variations in the method described in the above nonlimiting examples will suggest themselves to those skilled in the art and my invention is as claimed.

1 claim:

1. A method for forming wood which comprises impregnating the wood to be formed with a lower-alkyl amine containing 1 or 2 carbon atoms, bringing the impregnated wood to a desired configuration and drying the wood while maintained in the desired configuration.

2. A method according to claim 1 wherein impregnation is effected with an aqueous solution of the amine at ambient conditions. 5

3. A method according to claim 2 wherein the amine is methylamine. 

1. A method for forming wood which comprises impregnating the wood to be formed with a lower-alkyl amine containing 1 or 2 carbon atoms, bringing the impregnated wood to a desired configuration and drying the wood while maintained in the desired configuration.
 2. A method according to claim 1 wherein impregnation is effected with an aqueous solution of the amine at ambient conditions. 